A new species of Lachesilla, from Cabrits National Park, St. John's Parish, Dominica, is here described and illustrated. The phallosome is V-shaped, and it is autapomorphic in having the distal ends of the apodeme arms articulated to each clasper. Based on these characters, a new species group is created, close to the L. forcepeta and L. palmera species groups (the latter also diagnosed in this paper). The holotype is deposited in the National Insect Collection (CNIN), Instituto de Biología, Universidad Nacional Autónoma de México, Mexico City.

I describe herein a new species of Lachesilla, the second known in Dominica, with a distinct autapomorphic character, so unique in the genus that it deserves the creation of a new species group. Lachesilla is a large and diverse genus (288 described species worldwide, plus about an additional hundred awaiting description [http://psocodea.speciesfile.org; Mockford and García Aldrete (2010); pers. inf.]), in which presently 17 species groups have been recognized (pers. inf.), some with only 1 species each (e.g. the L. cerorma, L. magnifica, L. patzunensis and L. szirakii species groups), ranging to large groups as L.forcepeta and L. pedicularia, with 94 and 81 described species respectively.

Material and methods

One male specimen was available for study. It was dissected in 80% ethyl alcohol and its head, wings, legs and genitalia were mounted on a slide in Canada Balsam. Color was recorded placing the whole specimen, before dissection, in 80 % ethyl alcohol under the dissecting microscope, illuminated with cold white light at 80X. Measurements of parts on the slide were taken with a filar micrometer whose measuring unit is 136 µm for wings, and 53 µm for other parts. Abbreviations of parts measured are the following: FW and HW: length of right fore- and hind- wings, F, T, t1 and t2: lengths of femur, tibia and tarsomeres 1 and 2 of right hind leg, ctt1: number of ctenidobothria on t1 of right hind leg, Mx4: length of fourth segment of right maxillary palp, f1...fn: lengths of flagellomeres 1...n of right antenna, IO, D and d: minimum distance between compound eyes, antero-posterior diameter and transverse diameter, respectively, of right compound eye, all in dorsal view of head, PO: d/D. The holotype is deposited in the National Insect Collection (coden CNIN for Colección Nacional de Insectos), housed in the Instituto de Biología, Universidad Nacional Autónoma de México, Mexico City.

Etymology. The specific name refers to the articulation between the distal ends of the arms of the phallosome and the claspers, reminiscent of the sterno-clavicular joint in man.

Remarks

In the large genus Lachesilla, the males of the species in the L. forcepeta (García Aldrete,1974; Mockford, 1993) and L. palmera (diagnosed below) species groups, and in L. clavicularis, present the same structural plan of the male genitalia. However, males of the species in the L.forcepeta species group do not have a mesal prong in the paraprocts; except for some species with a short, sclerotized mesal prong in each paraproct. In some species, the male epiproct is either extended posteriorly, or presents 1 or 2 sclerotixed posterior projections; in most species, however, the epiproct is simple, not extended posteriorly and without projections. On this basis, it seemed sensible to withdraw, from species group forcepeta the species indicated below, to erect the species group palmera, diagnosed as follows:

L. palmera species group. With the characters of the L.forcepeta species group, but with males having a well defined mesal paraproctal prong, and epiproct either extended posteriorly in the middle or with 1 or 2 sclerotized posterior projections. Included species: L. acuminiproctus García Aldrete, L. amarilla New, L. capreola New, L. palmera New, L. bicornata New & Thornton, and L. pereirorum García Aldrete.

In the species of this group, the males have the phallosome apodemes fused to form a long, slender baculum, T-shaped distally (L. acuminiproctus), ending in a pointed apophysis (L. amarilla and L. pereirorum ), or divided distally, with a membranous lamella on each side. The claspers of the males in this group are either basally stout, with numerous setae and with the distal half pointed (l. acuminiproctus and L. bicornata), or they are long, slender (L. palmera), and with lateral, pointed apophyses (L.amarilla, L. capreola, and L. pereirorum). These characters differ from the V-shaped phallosome apodemes and from the claspers of L. clavicularis (basally slender, with a single seta, and with the distal half slender and distally acuminate). Lachesilla clavicularis is close to species group L. palmera, but cannot be assigned to it, or in the L.forcepeta species group, mainly on the basis of the V-shaped phallosome, and to the unique articulation of the branches of the phallosome with an excavation of the claspers, that deserves the creation of a new species group, diagnosed as follows:

L. clavicularis species group.With the characters of the L.palmera species group, but having the phallosome apodemes V-shaped, each branch articulating with an excavation of the clasper, unique in the genus (see Fig. 2).

I am grateful to Will K. Reeves, formerly of Clemson University, North Carolina, for making available for study the specimen of the species here described, as well as numerous specimens of Psocoptera collected in Dominica. Felipe Villegas (Instituto de Biología, UNAM), built the plate with my original illustrations. I also thank the Instituto de Biología, Universidad Nacional Autónoma de México, for continuous support to my research throughout the years.

Mockford, E. L. and A. N. García Aldrete. 2010. A new species of Lachesilla Westwood (Psocoptera: Lachesillidae) in the andra group with a proposed classification of the andra group. Zootaxa 2335:49-58. [ Links ]